Remote control system for electrical apparatus



Jan. 28, 1969 H. E. HOWLETT REMOTE CONTROL SYSTEM FOR ELECTRICAL APPARATUS Filed Dec. 29, 1965 u v n v A m n n \w um \mfi h h n h \s u 3 w u u is. n m 8 A A A a .u

...lI.- |ll||li rliie. Ill IIVIQ lllllllllll lib t=wsom 80S United States Patent Oflice 3,424,919 Patented Jan. 28, 1969 8 Claims ABSTRACT OF THE DISCLOSURE A remote control system for operating electric apparatus such as a motor having a remote control station including an apparatus status indicator such as a pilot light. A control unit is provided together with means for operating same either at the location of the electrical apparatus or at the remote station. The control unit includes a control relay coupled by a pair of conductors to the remote control station, which includes a remote power source and on-off switching means such as a startstop switch for selectively energizing and de-energizing the control relay. The pilot lamp at the remote station is connected across the pair of conductors in parallel with the control relay so that it is energized only when current flows in the control relay. An apparatus starting circuit is also provided which includes an apparatus power source and a control switch operable by the control relay of the control unit. Operation of the control switch completes the apparatus starting circuit thereby connecting the apparatus power source to the apparatus. The apparatus starting circuit also controls an auxiliary switch which is connected in circuit to the control unit for selectively completing the control circuit only when the apparatus starting circuit is complete. Coupling means such as a transformer is provided for coupling power from the apparatus power source to the control unit when the apparatus starting circuit is complete, the secondary circuit of the transformer including said auxiliary switch. The power coupled to the control unit by the transformer maintains the control relay energized after removal of the remote power source by release of the start switch so that the control switch as well as the relay switch is maintained closed, thereby maintaining continued energization of the apparatus.

This invention relates to an electrical apparatus control system and more particularly to an improved electrical apparatus control system operable from a remote control station.

Remote control operation of electrical apparatus such as a motor or motors has been accomplished with a variety of different electrical systems. The most common system for controlling a motor from a remote location utilizes four wire conductors between the remote control station and the motor location. One of these wires is usually a heavy gauge power source conductor and the other three comprise a separate heavy gauge conductor for momentarily applying the power to the motor starter at the motor through a start switch at the remote control station, a separate heavy gauge wire for momentarily interrupting the power to the motor starter through a stop switch at the remote control station, and one wire for status indication of the motor, that is, an indication of whether the motor is running or stopped. It will be appreciated that considerable conductor wire is involved in a four wire system where the remote control station is located at some distance from the motor to be controlled, and that three of the four wires must be heavy gauge wire to carry the current necessary to activate the motor starter. Thus the conventional remote control system requires a great length of heavy gauge wire. A reduction in either the total length of wire or in the size of the wire could represent considerable savings. The present invention makes possible a reduction in both total length and size of wire. The savings effected because of the reduction in wire size and length utilizing the remote control system of the present invention can best be appreciated in a multiple motor situation. Whereas the savings in conductor cost in a single motor remote control system over the prior art may be expressed as a 2 wire versus 4 wire savings, the savings in an n motor arrangement may be expressed as a n 1 versus 4n savings. Thus, the savings in a 10 motor arrangement could be expressed as an 1 1 conductor versus 40 conductor savings, or approximately a 72.5% savings.

There are some existing remote motor control systems which achieve a reduction in both length and size of wire, but they have proved to be unreliable in operation, especially those systems which utilize voltage sensitive components such as diodes which fail in field operations because of voltage surges introduced during lightning storms.

It is an object of the present invention to provide a remote control system for electric apparatus which reduces the number of electrical conductors between the remote control station and the apparatus.

It is another object of the present invention to provide a remote control system for electric apparatus in which the size of the electrical conductors between the remote control station and the apparatus is reduced.

It is another object of the invention to provide a remote control system for operating electric apparatus which utilizes fewer and more reliable components and is relatively insensitive to voltage surges such as might be caused by lightning.

It is a further object of the invention to provide a remote control system for electrical apparatus in which the remote power source is used only for starting the apparatus and status indicator lamp, the apparatus power source being used for continued operation of the apparatus and status indicator lamp.

According to the invention, there is provided in a remote control system for operating electrical apparatus a control unit and a remote control station. The control unit includes a control relay, and the remote control station includes a remote power source and on-off switching means, designated start-stop means where the electrical apparatus is an electric motor as shown, for selectively energizing and deenergizing the relay and a means for indicating the operating condition of the apparatus. An apparatus starting circuit is also provided which includes an apparatus power source and a control switch operable by the control relay connected in the control unit. The control switch when operated completes the apparatus starting circuit thereby connecting the apparatus power source to the apparatus. An auxiliary switch is provided which is connected to the control unit and which is enabled only when the apparatus starting circuit is complete. Coupling means are provided located in the control unit for coupling power from the apparatus power source to the control unit when the apparatus starting circuit is complete. The power coupled into said control unit maintains the control relay energized after removal of the remote power source to hold the control switch closed thereby maintaining the starting circuit complete to keep the apparatus energized.

The above mentioned and other features and objectives of this invention and the manner of obtaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawing wherein:

The single figure of the drawing is a schematic circuit diagram of the remote control system of the present invention.

The following is a description of an embodiment of the invention wherein the remote control system is con trolling an electric motor.

The remote control station is shown as broken line box 13. The remote power supply 14 is shown connected to one terminal of momentary contact start button 15 by electrical conductor 16. The electrical conductor 18 which connects the remote control station to the motor control unit 32 is connected to another terminal of the start button 15. Also connected to the remote power supply 14 is a second conductor 20 which is maintained at ground potential by the ground connection 22. Electrical conductor 20 extends from the remote control station 13 to the motor control unit 32 similarly to electrical conductor 18 thereby forming a pair of conductors. An electrical connection 24 extends from electrical conductor 20 to one terminal of a stop button 26. The other terminal of stop button 26 is connected via an electrical conductor 25 to a terminal of a second pair of terminals of start button 15, the other terminal of which is connected to conductor 18 via conductor 27. The second pair of terminals are connected by a connector 28 across the terminals when the start button is unoperated and which connector is removed when the start button is operated. It can be seen that the operation of stop button 26 would normally complete the path between conductors 18 and 20. However, operation of the stop button 26 would be overridden by an operation of the start button 15 which would break the electrical path between conductors 18 and 20 by removing connector 28 from its normal position across the second pair of terminals of start button 15. Thus, it can be seen that the start button 15 and stop button 26 cannot be effective at the same time. A status indicator lamp 30 is connected in parallel across conductors 18 and 20. It lights and remains lit as long as start button 15 is held down thereby serving as a check on the operability of the status lamp. The pair of electrical conductors 18 and 20 have connected thereacross in the control unit 32 a control relay 34. Upon depressing the start button 15, the power from the power supply 14 will be connected via electrical conductors 16 and 18 to one terminal of the control relay 34 while the other terminal of said relay is connected to the common ground electrical conductor 20. This will cause energization of the relay 34 which operates an associated switch 36.

The switch 36 associated with relay 34 is connected to a motor starting unit 40 which includes the usual starting coil 42, overload relay 44, and motor power switches 45, 46 and 47 which are operated by energization of starting coil 42. The starting unit is the standard combination magnetic motor starter such as is manufactured by General Electric Company and Westinghouse Corporation.

The motor starting unit has applied thereto three phase power via leads 50, 51 and 52 for operating the motor being controlled. The power from lead 50 passes thru a conductor 54 which is connected to one terminal of a stop button 56 located in a local control station 81. The other terminal of the stop button is connected to a terminal of control switch 36 via a conductor 58. The stop button 56 in its normal unoperated condition has its terminals connected together to provide an electrical path thru the stop button. The other terminal of control switch 36 is connected to a terminal of starting coil 42 -via conductor 60. The other terminal of starting coil 42 is connected via conductor 62 and overload switch 44 to conductor 51. Energization of starting coil 42 operates the associated switches 45, 46 and 47 and auxiliary switch 72. Each of switches 45, 46 and 47 are located in power leads 50, 51 and 52, respectively.

In operation, start button 15 is depressed, completing a circuit to A.C. supply 14 to thus energize control relay 34. The energization of control relay 34 operates associated switch 36. Operation of switch 36 completes the motor starting circuit which extends from the motor power source thru conductor 50, conductor 54, stop button 56, conductor 58, operated control switch 36, conductr 60, starting coil 42, overload switch 44, conductor 62 and conductor 51 back to the motor power supply. This completed motor starter circuit provides the energization for starter coil 42 which causes the enabling of associated switches 45, 46 and 47 which complete the connection of the three phase motor power supply via the electrical conductors 50, 51 and 52 to the motor proper for operation thereof.

An electrical conductor 64 extends from one terminal of starter coil 42 to one terminal of the primary of a control transformer 66 located in control unit 32. The other terminal of the primary of control transformer 66 is connected to the other terminal of starter coil 42 via the electrical conductors 68 and 62. Control transformer 66 is a step down transformer which couples the voltage in the motor starting circuit to the control circuit of control unit 32. The motor power supply is a 220 volt source whereas the control circuit of the control unit 32 operates at volts. Thus, the primary to secondary winding ratio of the transformer will be such as to step down the voltage to the correct value. The secondary of the transformer has one terminal connected via electrical conductor 70 to one terminal of control relay 34 while the other terminal of the secondary of the control transformer 66 is connected via conductor 74 to a terminal of an auxiliary switch 72 which is controlled by the starting coil 42. A resistor 76 of suitable resistance, preferably 400 ohms, is connected in series in the electrical conductor 74. The other terminal of switch 74 is connected to the other terminal of control relay 34. Thus, the control circuit of control unit 32 extends from the secondary of control transformer 66 through conductor 70, control relay 34, auxiliary switch 72, resistance 76 and back to the secondary of the transformer 66. When auxiliary switch 72 is enabled by the energization of starting coil 42 the control circuit is complete and control relay 34 is maintained in its energized condition, having been already energized by the remote power supply 14 through momentary contact start button 15 at the remote control station. Thus, it can be seen that control relay 34 is common to both the remote control station circuit and the control circuit of control unit 32. The control relay 34 is energized by start button 15 from the remote control station 13 and is maintained in its energized condition after the removal of the power from the remote control station 13 by the control circuit of the control unit 32 which derives its energization from the motor power supply through the motor starting circuit which is only completed when switch 36 of the motor starting circuit is enabled by its associated control relay 34 in the control circuit. Likewise, the control relay 34 is only maintained energized as long as starting coil 42 is energized to hold auxiliary switch 72 in its enabled condition.

It will be appreciated that the voltage induced in the secondary of control transformer 66 is not only applied across control relay 34 but also is applied across status indicator lamp 30 which is located in the remote control station and which is connected in parallel with control relay 34. Thus, the control transformer secondary voltage is applied over conductor 18 and common ground conductor 20 to complete a circuit to supply the power to operate status indicator lamp 30.

The electrical connections and the operation of the circuits have been described above in connection with the operation of start button 15 at the remote control station 13. Operating stop button 26 at the remote control station 13 will provide a short circuit path between conductor 18 and conductor 20 such that the power applied across control relay 34 derived from the secondary of control transformer 66 will be short circuited thru connector 28 of start button 15, conductor 25, stop button 26 and conductor 24. A resistor 76 of suitable value, preferably 400 ohms, is located in the control circuit of control unit 32 to limit the current when a short circuiting of the control relay 34 takes place by operating the stop button 26. Also, resistor 76 limits the current in a situation where the motor power supply voltage is coupled to the control circuit via control transformer 66 and simultaneously the remote power supply voltage is connected to the control circuit of control unit 32 via the pair of leads 18 and 20 and where these two voltages are out of phase. This situation may exist in the overlap period after control switch 36 and auxiliary switch 72 have closed and prior to the release of start button 15 or if the start button is pressed when the motor is running. Once the short circuit path is complete the control relay 34 will be deenergized opening switch 36 in the motor starting circuit of motor starter 40 causing the starter coil 42 to deenerg'ize and consequently stop the motor. Once the starter coil 42 is deenergized the auxiliary switch 72 will be disabled thus rendering the control circuit of the control unit 32 open and thus unable to maintain the voltage across the control relay 34. Since voltage is not applied across the control relay 34 due to the open condition of the control circuit because of the disabling of the auxiliary switch 72 the motor status lamp 30 which is connected in parallel with the control relay 34 will also have no voltage thereacross and accordingly will not be lit. It should be noted that the remote motor control system is now in its initial condition ready for a further start operation.

A local control station 81 is provided which consists essentially of a start button 82 and stop button 56. As previously mentioned the stop button 56 is utilized in the motor starting circuit and in its normal condition is engaged, that is, provides a through conduction. Operating the start button 82 completes the connection from the motor power source via conductor 50, conductor 54, stop button 56, conductor 84, start button 82, and conductor 86, which connects to conductor 64 and one terminal of starting coil 42, the other terminal of 42 being connected to the power source via conductor 51. The operation of the start button 82 provides an alternative path for the motor starting circuit rather than connecting to the starter coil through conductor 58 and the control switch 36 of control relay 34. Regardless of whether control relay 34 and its associated switch 36 is energized or not, the operation of start button 82 provides voltage across starter coil 42 to start the motor. Once the motor starts switch 36 will close because of the energization of control relay 34 by the power from the motor power source coupled into the control circuit. Likewise, operation of stop button 56 opens the motor starting circuit thus deenergizing starting coil 42 which disables the power switches 45, 46 and 47 thereby stopping the motor.

The remote control system described herein is obviously not limited to remotely controlling electric motors but can be easily adapted for remote control operation of practically any electrical apparatus operating at any voltage.

Obviously, many modifications and variations of the invention as hereinabove set forth, may be made without departing from the spirit and scope thereof, and therefore. only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In a remote control system for operating electric apparatus, a control circuit including a control relay, a remote control station including a remote power source and on-off switching means for selectively energizing and deenergizing said relay, an apparatus starting circuit including an apparatus power source, means for selectively connecting said power source to said electric apparatus comprising a control switch operable by said control relay and connected in said apparatus starting circuit for completing said apparatus starting circuit, coupling means connected to said control circuit, means including said coupling means for selectively coupling power from the apparatus power source to said control circuit only when said apparatus starting circuit is complete, an auxiliary switch located in said control circuit for selectively completing said control circuit, means responsive to energization of said starting circuit for controlling said auxiliary switch so that said control circuit is complete only when the apparatus starting circuit is complete, said coupled power from said apparatus power source providing the power in said control circuit for maintaining the energization of said control relay after the disconnecting of said remote power source to hold said control switch closed thereby maintaining said starting circuit complete to keep the apparatus energized.

2. A remote control system according to claim 1, wherein said circuit coupling means comprises a transformer having a primary to secondary winding ratio to change the apparatus power supply voltage to a voltage level equal to the remote power source voltage and to isolate the apparatus power supply voltage from ground potential.

3. In a remote control system according to claim 1, wherein said electric apparatus comprises an electric motor having a starting coil and wherein a local startstop means is provided for operating the apparatus independent of said remote on-olf switching means, the local start means comprising a button which when energized completes a circuit from the apparatus power supply to said starting coil and associated switches which connect the apparatus power supply to said electric motor apparatus, said local stop means normally connecting the ap paratus power supply to said apparatus starting coil through said control relay switch in said starting circuit, said local stop means when operated interrupting said starting circuit to disconnect the apparatus power supply from said apparatus starting coil thereby stopping said apparatus.

4. In a remote control system according to claim 1, wherein said control circuit is connected to said remote control station by a pair of electrical conductors, and said off means in said remote control station is connected across said pair of conductors in parallel with said control relay to provide a short circuit path for the power coupled to said control circuit from said apparatus power source thereby deenergizing said control relay and opening said control switch and said starting circuit to stop the apparatus.

5. In a remote control system according to claim 4, wherein a status indicator is provided in said remote control station connected across said pair of conductors in parallel with said control relay, said status indicator being energized by the power coupled to said control circuit from said apparatus power source to indicate the apparatus operating.

6. In a remote control system according to claim 4, wherein a resistor of suitable resistance is connected in said control circuit to limit the current flow therein when the control relay is short circuited by said off means and when said apparatus power supply and said remote power supply are connected simultaneously out of phase in said control circuit.

7. In a remote control system according to claim 5, wherein said status indicator at said remote location is a lamp, the on condition thereof representing the apparatus energized and the ofi condition thereof indicating the apparatus deenergized.

8. In a remotely operable electrical apparatus control system having a remote control station including an apparatus status indicator, a remote voltage source for initiating said apparatus operation and on-off switching control means, a control circuit connected to said remote control station by a pair of electrical conductors, one of said pair of electrical conductors being maintained at ground potential, a control relay connected to both said remote control station and said control circuit, said control relay being connected across said pair of electrical conductors and operable by said on-olf means at said remote control station, means comprising an apparatus starting circuit including an apparatus starting coil and associated apparatus switches for connecting an apparatus power supply to the apparatus, means comprising a control switch connected in said apparatus starting circuit and operable by said control relay for completing the starting circuit to connect said apparatus power supply to said apparatus, said control circuit including a circuit coupling means for coupling the voltage in said apparatus starting circuit to said control circuit, means comprising a further apparatus switch connected in said control circuit and operable by energization of said apparatus coil to complete when energized a connection between the circuit coupling means and said control relay thereby completing said control circuit and maintaining said control relay energized after the remote power supply connection has been interrupted, said status indicator located in said remote control station being connected across said pair of conductors in parallel with said control relay thereby being energized when said control circuit is complete to indicate the energization of the apparatus being controlled, said otr' means located in said remote station being connected across said pair of conductors in parallel with said control relay to short circuit when energized the control relay thereby disabling the control relay switch in said apparatus starting circuit deenergizing the apparatus and disabling the further apparatus switch to open the control circuit thereby deenergizing said control relay and said status indicator at said remote station.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner.

T. B. JOIKE, Assistant Examiner.

US. Cl. X.R.

NITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,424,919 January 28, 1969 Harry E Howlett It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8, line 11, cancel "No references cited." and insert References Cited United States Patents 2,477,166 7/1949 Berry et a]. 307-14OX 2,743,399 4/1956 Derr et a1. 317-136X 2,905,870 9/1959 Henderson, Jr. 317-136X Signed and sealed this 17th day of March 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Commissioner of Patents Edtvard M. Fletcher, Jr.

Attesting Officer 

